Effect of intraoperative radiotherapy in the treatment of retroperitoneal sarcoma

Current National Comprehensive Cancer Network guidelines for the treatment of retroperitoneal sarcomas (RPS) endorse surgical resection, but the role of radiotherapy (RT) is less clear. We investigate the utilization and benefits of intraoperative RT (IORT) in the treatment of RPS.

We queried the Surveillance, Epidemiology and End Results (SEER) database (1988-2013) for the utilization of IORT and perioperative external beam RT (EBRT) in patients who underwent surgical resection of RPS. Groups were defined as any IORT (aIORT), IORT alone (IORT-), IORT with EBRT (IORT+) and preoperative and/or postoperative EBRT without IORT (EBRT). Demographics, tumor characteristics, extent of disease, and survival were compared between groups.

We identified 908 patients with RPS who underwent surgical resection with perioperative RT. Demographics of age, sex, and race were similar between groups. There was no difference in baseline tumor characteristics of mean size, tumor grade, or histological subtype between groups. A higher percentage of patients receiving aIORT had tumors >20 cm in size, and extension beyond local tissues. Liposarcoma and leiomyosarcoma were the most common subtypes overall and in each subgroup. Patients with liposarcoma undergoing IORT and EBRT (IORT+) demonstrated a survival benefit over both IORT alone (IORT-) and EBRT alone.

IORT was used infrequently for RPS but generated equivalent outcomes compared to EBRT, despite being utilized more often for larger tumors and those with peri-tumoral soft-tissue invasion. Patients with the most common subtype (liposarcoma) may benefit from combination IORT with adjuvant EBRT versus other regimens.